On the Nature of Human Romantic Interaction: According to Variety, Warner Bros. Pictures has optioned feature rights to Karl Iagnemma's short story "On the Nature of Human Romantic Interaction," which Heyday Film and Plan B Entertainment will produce.

In "Interaction," which appears in the author's short-story collection of the same name, a young academic tries to formulate a series of mathematical equations that will force his randy girlfriend to make a commitment to him.

Kiernan and Michele Mulroney will script. Producers are David Heyman, Brad Grey, Brad Pitt and Jennifer Aniston. Guymon Casady will exec produce.

Warners senior VP of production Greg Silverman will oversee the project. Dede Gardner oversees for Plan B.

The Mulroneys are slated to make their directorial bow next spring with Paper Man, which they also wrote. Sideways star Paul Giamatti is attached to topline.

After Brad Pitt read the Paper Man script, he brought the Mulroneys aboard for production rewrite work on Mr. and Mrs. Smith. The couple also adapted Matthew Sharpe's novel "Sleeping Father" for Warners.

Published last year by Dial Press, "On the Nature of Human Romantic Interaction" was Iagnemma's first published fiction collection. The award-winning writer is also a research scientist at MIT.